This invention relates to generator stators and, more specifically, to a wedge and slide system used at the ends of the stator core. The wedge and slide system is adjustable to permit in situ radial correction for radial pressure and dimension losses which occur over time.
Electric utility companies require large turbine-generators to operate reliably for long periods of time, for example, thirty years or more. Normal, steady-state electromagnetic forces acting on the armature winding are capable of causing armature bar vibration within a much shorter period than the expected generator lifetime. Armature bar vibration can occur if radial clearances are present within the stator core slot. Bar vibration can result in armature bar insulation abrasion. The abrasion can become severe if maintenance actions are not taken to retighten the slot support system and arrest the vibration. Typically, a prolonged maintenance outage is required to retighten the slot support system and eliminate radial clearances within the slot.
The electrical windings at opposite axial ends of the stator core slots may be particularly susceptible to accelerated abrasion due to: 1) pre-existing or rapidly-evolving radial clearances, 2) the effects of excessive or continuous oil contamination, 3) the effects of end winding electromagnetic forces, and 4) abnormally-high electromagnetic design forces on the slot portion of the winding. It is therefore important to provide an in situ means for eliminating radial clearances that develop in this location in order to prevent unscheduled or prolonged service outages.
In an attempt to address these problems, a stepped wedge and slide arrangement is proposed in U.S. Pat. No. 4,149,101 but for the purpose of preventing axial displacement of wedges within the core slot. A stepped bracing arrangement is proposed in U.S. Pat. No. 3,842,303 but in the context of an end winding support fit-up device between the coil end arms.